Alarm over "pig MRSA" — but not in the US

There’s some new news out — along with a fair amount of public reaction — regarding “pig MRSA” or, to use the technical term, MRSA ST398, the “third epidemic” strain that emerged in pigs in the Netherlands in 2004 and has since appeared, in animals, retail meat, and humans, across the European Union, in Canada, and in the United States. (My last post on it is here, and a long archive of my posts on it starts here.)

I wish I could say the attention to ST398 was being paid in the United States, where there is almost certainly more MRSA in livestock than has been recorded, given that the only published surveillance, from 2009, covered only Iowa and Illinois. Unfortunately, there is still no indication that federal agencies have any intention to test for the presence of the organism in animals or in meat. In fact, the major surveillance mechanism for drug-resistant organisms in meat animals, retail meat and meat-eaters in the US, the National Antimicrobial Resistance Monitoring System or NARMS, doesn’t test for MRSA at all; it handles only enteric or gut-borne bacteria such as Salmonella and Campylobacter. (NARMS IS shared among three agencies: the CDC handles drug-resistant foodborne bacteria in humans, the FDA looks for the same bacteria in food, and the USDA looks for those bacteria being carried by livestock.)

Instead, as so often seems to happen with antibiotic resistance, the country paying attention is in Scandinavia — in this case, Denmark. The annual report from Denmark’s surveillance scheme, DANMAP (Danish Integrated Antimicrobial Resistance Monitoring and Research Programme) is out. Denmark does surveil for MRSA, and here’s what they found: 13% of pigs, at slaughter, were positive for MRSA ST398.

The Danes are very clear where they think this is coming from:

In 2009, the total consumption of antimicrobial agents in animals amounted to 129.7 tonnes. This was a 10.4% increase compared with 2008. The increase could mainly be attributed to consumption in pigs. An increasing number of pigs were exported at 30 kg live weight. When we adjust the statistic for this, we find that antimicrobial consumption in pigs increased by 12.7% from 2008 to 2009… The increase could largely be attributed to tetracyclines (12%), macrolides (16%) and pleuromutilins; these antimicrobial agents are commonly used for mass medication in feed or drinking water in pig herds with disease problems. (DANMAP Annual Report 2009, p.15)

It is important to note that there is no clear evidence that MRSA ST398 in animals is causing human cases in Denmark (though such cases have been recorded in numerous other countries). But despite the presence of MRSA ST398 in its pigs, Denmark is not the perfect natural laboratory for assessing the risk, because — thanks to aggressive infection control in hospitals and antibiotic conservation in the community — MRSA simply doesn’t spread much there; the country’s overall MRSA epidemic is very small. However, there is clear attention being paid to the possibility: the DANMAP report notes: “In Danish meat MRSA was found in 4.6%, 1.4% and 0% of pork, beef and (chicken) broiler meat, respectively. In imported meat the occurrence was 7.5%, 0% and 18% in pork, beef and broiler meat, respectively.”

This MRSA finding was huge news in Denmark over the past 10 days. It was covered by the newspapers Politiken (via cartoon), Arhus Stifstidende (in an editorial) and the Copenhagen Post (in English); the business publication Ingenioren (Danish) which accused the minister of food of “waffling” on the seriousness of the situation; the broadcast network DR (Danish); and the news site 24timer (Danish).

It was also covered by the Norwegian farm publication Norsk Landbruk, which picked apart the statistics in the DANMAP report to show that Denmark’s rate of MRSA in pigs was 4x greater than an EU-wide estimate from just one year earlier.

This burst of news and reaction from Denmark makes it clear — as though it weren’t already — that there are places in the world which take the emergence of MRSA in farm animals, as a result of farm antibiotic use, to be a very serious issue. Surely it’s time for the US to take this seriously as well.